1. Field of the Invention
This invention relates to a stretchable nonwoven web containing multiple component fibers which comprise an elastomeric polymeric core and polymeric wings attached to the core wherein the wing polymer is either non-elastomeric or is less elastic than the core polymer. After suitable heat-treatment, the multiple component fibers form spiral twist and can also develop three-dimensional crimp.
2. Description of Related Art
Stretchable nonwoven fabrics are known in the art. For example U.S. Pat. No. 5,997,989 to Gessner et al. discloses a spunbond elastic nonwoven fabric comprising a web of bonded filaments of thermoplastic elastomer which is prepared in a slot draw spunbonding process operated at a rate of less than about 2000 meters per minute. Elastomeric meltblown webs are also known, for example meltblown webs of polyetherester polymers are described in U.S. Pat. No. 4,741,949 to Morman et al.
Nonwovens formed from elastomeric polymers generally have an undesirable rubber-like hand and therefore are often used in laminates wherein the elastomeric web is bonded on one or both sides to a non-elastomeric layer such as in a stretch-bonded or neck-bonded composite laminate. Nonwovens formed using a high content of elastomeric polymer are generally expensive because of the high cost of many elastomeric polymers. Layers of elastomeric webs also tend to adhere to one another, for example when wound on a roll, a phenomenon known in the art as “blocking”.
Multiple component fibers comprising an elastomeric component and a non-elastomeric component are known in the art. For example, U.S. Pat. No. 4,861,660 to Ishii describes composite filaments suitable for preparing stretchable woven and knitted fabrics.
Nonwoven fabrics comprising laterally eccentric multiple component fibers comprising two or more synthetic components that differ in their ability to shrink are also known in the art. Such fibers develop three-dimensional helical crimp when the crimp is activated by subjecting the fibers to shrinking conditions in an essentially tensionless state. Helical crimp is distinguished from the two-dimensional crimp of mechanically crimped fibers such as stuffer-box crimped fibers. Helically crimped fibers generally stretch and recover in a spring-like fashion.
U.S. Pat. No. 4,405,686 to Kuroda et al. describes a highly stretchable conjugate filamentary yarn which is prepared from composite components respectively comprising a thermoplastic elastomer and non-elastomeric polyamide or polyester, each of the individual constituents having a cross-section of a compressed flat shape.
U.S. Pat. No. 6,225,243 to Austin describes a bonded web of multi-component strands that include a first polymeric component and a second polymeric component having an elasticity that is less than the first polymeric component.
There remains a need for elastic nonwoven fabrics having a high degree of recoverable elongation which also have improved hand and lower overall fabric cost than elastic nonwoven fabrics currently known in the art.